Piston assembly



July 19, 1927.

. w. PRELLWITZ PISTON ASSEMBLY Filed Auz. 4, 1926 INVENTOR. 14 i! mPnel am H15 AfTOIZf Patented July 19, 1927. 1

UNITED STATES PATENT OFFICE.

WILLIAM PRELLW'ITZ, OF EAS'ION, PENNSYLVANIA, ASSIGNOE 'IO INGERSOLL-RANLD COMPANY, OF JERSEY CITY, NE'W JERSEY, A CORPORATION OF NEW J EBSEY.

PISTON ASSEMBLY.

Application filed August 4, 1926. Serial No. 127,055.

This invention relates to pistons, but more particularly toa dilterential type ct piston in which the portions of different diameters are formed separately and are held in as sembled relationship with respect to each other by suitable clamping means.

The present invention is particularly ap-. plicable to compressors of the multistage type in which the several cylinders lie in the same longitudinal plane.

One object of the invention is to render the piston assembly flexible so that the several portions or members comprising the piston may adjustthemselves in theii re spective cylinders when the diameters of the members change due to variations in tem perature and other causes of disalignment.

Another object is to prevent relative longitudinal movement between. the various members which coniipii'ise the piston.

Other objects will appear hereinafter.

The invention consists of the combinations of elements, features of construction and arrangement of parts substantially as hereinafter described and more particularly pointed out in the appended claims and illustrated in the accompanying drawings, in which Figure 1 is a sectional elevation of a plurality of cylinder chambers in which arranged a piston constructed in accordance with the practice of the invention. and

Figure 2 is a longitudinal elevation in section of a modified form of piston.

Referring to the drawings, A represents an intermediate cylinder to the ends ot which are secured cylinders B and C. The cylinders B and C may be secured to the cylinder A in any suitable manner, in this instance tap bolts D being used for this purpose. These cylinders are of the type commonly used in multi-stage compressors, the usual inlet and exhaust valves being omitted from the drawings for the sake of simplicity of illustration.

In machines of this type, relative disalignment between the several cylinders is at times caused by unequal expansion. and contraction of these elements due to variations in temperature. It therefore he quently happens that one or the other of the cylinders, together with the piston reciprocating therein, is subjected to higher temperatures, due to the heat of compression and other causes than the adjacent cylinders. As a result, the cylinder thus subjected will be drawn out of alignment with the adjacent cylinders, thus causing the pis-- ton reciprocating therein to bind on the walls thereof. In order to'overcome this objectionable feature in the present instance, a piston member E dividing the cylinder A into a low pressure chamber F and a second stage chamber G is provided with annular grooves H and J in its ends to receive slidably annular projections K and L oi? piston members 0 and P reciprocating in the cylinders B and C respectively. It is of course to be understood that there is ample clearance between the annular projections and the walls of the grooves H and J to prevent binding at these points whenever con-- ditions are such that the piston members 0 and P are caused to incline from the longitudinal axis of the piston assembly. A rod. Q, which may be the piston rod of the compressor extends through the members l5. 0 and P for connecting them together.

In order to permit relative axial dis-alignment oil. the piston members with respect to each other so that the said members may adjust themselves in their respective cylin ders, the rod Q is provided with an intermediate tapered portion R to cooperate with a tapered bore S formed in the member E. The tapered bore S extends only partly through the member E and from the small end of said bore to the opposite end oi the member is formed a straight bore T to receive a straight portion U of the rod Q. In the present instance the outer end of the straight portion U is threaded to receive a nut V which bears against the end of the member E for holding said member firmly in assembled position on the rod Q. A portion W of the rod Q adjacent the tapered portion R is preferably of smaller diameter than the large end of the tapered bore R to render said portion W flexible and thus also to prevent contact with the walls of straight bore X in the member P through which the portion W extends.

At the outer end of the portion IV of the rod Q, is formed a tapered portion Y which cooperates with a tapered bore Z formed in the outer end of the member P for limiting endwise movement of the member P in the direction of the member E. A nut Z2 is in this instance screwed on the rod Q, to bear against the outer end of the member P for forcing said member firmly on the tapered portion Y.

The member is also provided with a ta pered bore cwhich cooperates with the tapered portion 6 at the end of the rod Q for limiting endwise movement of the member 0 in the direction of the intermediate member E. A straight bore f leading from the tapered bore (2 to the inner end 01? the menu her 0 is' preferably of somewhat larger di ameterhart that portion oil 1. rod w rh thcrethrouglii. to prcre. ,nntact be tween the Zrod and the wall of the bore The I er end oit the rod Q is threaded to receive a nut whereby themember may be forced firmly on the tapered portion a. By thus permitting only the outer end of the members 0 and P to contact with the rod Q, the rod may bend freely whenever one or the other, 'or both, of the said cuter members tend to incline froin the longitudinal axis of the intermediate member.

In the u'iodification illustrated in Figure a rod 17L having a tapered portion and reduced t I v:hndrical portion h extends through outer piston members 0 and y) and an intermediate member (1. In this instz'ince the inc er y is provide'd with a straight bore 1' Wllitfil'] cooperates closely with the redau'ed cylin clr' al extension 7.: and has cylindrical recer is s and t in its end faces to receive cylindrical. projections a and i) torn'icd'on the inner i zrcc of the members 0 and 7 respectively. The projections it and '0 are preferably of a slightly greater length han thc depth of the recesses s and tso that only the ends of said projections will abut the i'i'remher (1. v

Preferably, only the outer ends oi? the outer members 0 and 7) are permitted to contact with the red It, and to this end a tapered bore in is formed in the wall of the member 0 to cooperate with. the tapered portion A straight bore a; is formed in the outer end of the member y) to cooperate slidahly with the extension it. The outer end of the extension 713 may be screw threaded to receive a suitable nut i for holding the i'uen'il'iers firmly in assen'ibled position on the red It. The members 0 and y) are also provided with recess 5 2 and 2 to prevent contact between the said members and the rod hroughout the greater portion of thelength oi? said members, thus permitting the red It to bend readily whenever conditions in the cylinders and the piston are such that binding would occur it the piston were made ot a single piece.

I claim: c v

1. An adjustable piston, comprising an flexible to permit the outer members to incline from the longitudinal axis of the in.-- torinediato member, tapered portions on the rod to cooperz-i-te with tho-tapered bores for limiting endwise movement of the members in one direction with respect to each other,- and nuts on the rod for preventing relative longitudinal moren'ient between thenrembers in the opposite direction,

2. iin'a'djustahle piston, comprising an intermediate cylindrical member having annular grooves in its ends, a central. bore in said member, outer cylindrical members of smaller diameter at the ends of the interme.

diate member, annular projections on the outer members extending into the grooves for holding, the members normallydn c oaxial relationship with respect to each other,

a rod through the members contacting with the outer ends of the outer members and with the wall of the bore in the intermediate member, said rod being); flexible to permit the outer members to incline from the lonitudinal axis of the intermediate member, and means for preventing endwi'se movement of the members with respectto each other and with respect to the rod.

3. An adjustable piston, comprising an in- 'lOlJTlOClltt tG member having a tapered bore, outer members interlocked with the intermediate member to hold the members n-orn'ially in coaxial relationship with respect to each other said outer members having end tapered bores and straight bores of larger diameter than the tapered bore, a rod .o'l.

su'ialler diameter than the straight bores 0X tending through the n'i'embers, said rod be; ing flexible to permit relative axial disalign ment oil the members, an intermediate tapered portion on the rod to cooperate with the tapered bore in the intermediate member for limiting endwi'se movement of the intern'iediate member in onedirection with re tapered portions on the rod to cooperate with the tapered bores in .the outer members for limiting endwise movement of the outer members in the direction of theintermediate member and nuts screwed on the rod to bear against the members for holding the members on the rod. a

In testimony whereof I have signed this specification. I

WILLIAM PRELLWITZ.

spect tothe rod, outer oppositely extending 

